1. Field of the Invention
The present invention relates to an ink, an ink-jet recording process, and instrument making use of the ink. More particularly it relates to an ink, an ink-jet recording process, a recording unit, an ink-jet recording apparatus and an ink cartridge that are capable of achieving excellent anti-clogging and also making a good record even on non-coated paper such as wood free paper, medium wood free paper or bond paper, i.e., what is called plain paper, commonly used in offices and so forth.
2. Related Background Art
Inks with greatly various manners of composition have been hitherto reported with respect to inks for writing implements such as fountain pens, marking pens and water-based ink ball-point pens and inks for ink-jet recording.
In particular, in recent years, detailed research and development efforts have been made from various approaches such as composition and physical properties, with respect to inks for making a good record even on plain paper such as copy paper, reporting paper, notepaper or letter paper commongly used in offices.
For example, inks usually contain high-boiling organic solvents such as glycols for the purposes of anti-drying, anti-clogging and so forth. When recording is carried out using such inks on a plain paper having a high degree of sizing, ink does not readily penetrate into paper and the part on which a record has been made does not dry well, so that when recorded letters or the like are touched, the hand may be stained with ink or the letters are rubbed to become smeared. Thus, there has been a problem with respect to drying performance of this kind.
Under such circumstances, in order to increase the penetrability of ink into paper, Japanese Patent Application Laid-open No. 55-29546 proposes a method in which a surface active agent is added in ink in a large quantity. In such an instance, the following problems have been caused: feathering occurs very frequently on some kind of paper; when the ink is filled in writing implements, the ink falls in drops from the pen point; and when filled in an ink-jet recording head, the ink recedes from the orifice surface depending on the structural conditions of the head, resulting in no ejection of ink, or on the other hand the whole of the orifice surface becomes wet, also resulting in no ejection of ink.
Japanese Patent Application Laid-open No. 54-104933 and Japanese Patent Publication No. 62-14189 disclose a method in which N,N-bis(polyoxyethylene (or -propylene))-p-toluenesulfonamide is added to ink. According to this method the solubility of dyes can be effectively improved, but it is required to use in combination an organic solvent such as a polyhydric alcohol in a fairly large quantity, so that the method has the problem that the ink has a poor drying performance on a recording medium such as paper, and may cause a stain at a touch even after the lapse of a long period of time. For this reason, it is also required to use in combination a surface active agent in order to improve the penetrability into paper. As a result, feathering may occur to give an insufficient print quality level.
There is another problem that, when the ink is used in ink-jet recording and the ejection of ink is stopped, the above compound recedes from the orifice surface upon evaporation of water, etc., and hence has a poor anti-clogging performance.
Japanese Patent Application Laid-open No. 51-8031 discloses an ink in which a specific carboxylic acid amide derivative is mixed in a water-based ink so that its anti-drying performance can be improved. If, however, this ink is used in ink-jet recording, it is impossible to completely prevent clogging when the ink is ejected again after a pause of recording and also to obtain a superior print quality level.
Japanese Patent Application Laid-open No. 63-297477 also discloses a non-water-based ink in which a dicarboxylic acid diester and a specific carboxylic acid amide derivative are used in combination. It discloses that use of the non-water-based ink has solved the problem of clogging involved in water-based inks. The non-water-based ink, however, has a problem on the safety, and moreover has the disadvantages that it causes feathering very frequently when letters or the like are printed on plain paper, and also has a poor storage stability.
Besides the foregoing, various improvements have ever been attempted. Up to the present, however, no ink is known which can resolve all the problems with respect to the above drying performance, print quality level and also anti-clogging.